Question 1

In the reactivity series of metals, the most reactive metal among the following is:

Accepted Answer

potassium. Potassium is near the top of the reactivity series and is the most reactive of these.

Question 2

The least reactive metal among the following is:

Accepted Answer

gold. Gold is at the bottom of the reactivity series and is the least reactive.

Question 3

When an iron nail is dipped in copper sulphate solution, the blue colour fades and the nail turns brownish because:

Accepted Answer

iron is more reactive and displaces copper. Being more reactive, iron displaces copper from copper sulphate (Fe + CuSO₄ → FeSO₄ + Cu).

Question 4

Metals placed above hydrogen in the reactivity series can displace hydrogen from dilute acids. Which metal does NOT react with dilute hydrochloric acid?

Accepted Answer

Copper. Copper lies below hydrogen in the series, so it does not displace hydrogen from acids.

Question 5

Sodium and potassium are stored under kerosene because they:

Accepted Answer

react vigorously with air and water. These highly reactive metals react vigorously (even catch fire) with air and moisture, so they are kept under kerosene.

Question 6

A more reactive metal can displace a less reactive metal from its salt solution. Which pair will react?

Accepted Answer

Zinc added to copper sulphate solution. Zinc is more reactive than copper, so it displaces copper from copper sulphate.

Question 7

The correct order of decreasing reactivity is:

Accepted Answer

K > Na > Zn > Fe > Cu. The standard reactivity series decreases as K > Na > … > Zn > Fe > … > Cu.

Question 8

In the reactivity series of metals, which of the following metals is the most reactive?

Accepted Answer

Potassium. The reactivity series places the most reactive metals at the top. Potassium sits near the very top, while iron, copper and gold become progressively less reactive, with gold being one of the least reactive.

Question 9

An iron nail is dipped in blue copper sulphate solution. After some time the nail is coated with a reddish-brown layer and the blue colour fades. This happens because

Accepted Answer

iron is more reactive and displaces copper from the solution. Iron is more reactive than copper, so it displaces copper from copper sulphate solution. Reddish-brown copper deposits on the nail and pale green iron sulphate forms, which is why the blue colour fades.

Question 10

Which one of the following combinations will NOT produce a displacement reaction?

Accepted Answer

Copper added to iron sulphate solution. A metal can displace only a less reactive metal from its salt. Copper is less reactive than iron, so copper cannot displace iron from iron sulphate solution and no reaction takes place.

Question 11

Three metals P, Q and R are tested. P displaces Q from its salt solution, and Q displaces R from its salt solution, but R cannot displace P. Arrange the three metals in order of decreasing reactivity.

Accepted Answer

P > Q > R. A metal displaces a less reactive metal. Since P displaces Q, P is more reactive than Q; since Q displaces R, Q is more reactive than R. Therefore the order of decreasing reactivity is P > Q > R.

Question 12

Gold and silver are often found in nature in their free (uncombined) metallic state, whereas potassium and sodium are always found as compounds. The best explanation is that

Accepted Answer

gold and silver are very unreactive, so they do not readily form compounds. Very unreactive metals like gold and silver lie at the bottom of the reactivity series and do not readily react with air, water or other elements, so they occur free. Highly reactive metals such as sodium and potassium always occur combined as compounds.

Reactivity Series — Homi Bhabha Class 9 Chemistry MCQs with Solutions

Questions with solutions